Melanin from the fungus Gliocephalotrichum simplex protects seeds from the effects of exposure to gamma radiation

Protection of seeds from ionizing radiation is an important future need in space travel. We examined the usefulness of eumelanin from the fungus Gliocephalotrichum MTCC 5489 for this purpose. Seeds of Oryza sativa, Brassica nigra, Vigna radiata and V. aconitifolia were enclosed in Petri dishes coated with paint containing various concentrations of nanomelanin and exposed to doses of 0.1 to 2.0 kGy Cs-137 or 0.1 to 0.5 kGy Co-60 radiation. While Cs-137 radiation severely affected the rate of germination (germination index, GI) and germination percentage of Oryza sativa, whereas other seeds were less affected, Co-60 markedly diminished the GI of all the seeds. Increasing concentrations of melanin coating afforded significant protection to the GI of O. sativa seeds exposed to Cs-137 and to all seeds exposed to Co-60 radiation. The germination percentage of seeds was dose- and radiation dependent, with no effect observed for all doses of Cs-137 or 0.1 kGy Co-60 radiation, whereas 0.5 kGy Co-60 radiation killed 50 to 60% of the unprotected seeds. Melanin paint offered nearly 100% survival. This study demonstrated that melanin-containing materials can provide effective shielding from gamma radiation for diverse types of seeds that are important for human consumption, which has implications for space agriculture and agriculture in extreme environments.